An ink-jet printer is a known example of a liquid discharging apparatus that discharges ink onto various kinds of target objects such as a sheet of paper, cloth, film, and so on to perform printing. An ink-jet printer discharges ink through its nozzles to form dots on a target object for printing.
In such an ink-jet printer, an abnormal discharge phenomenon, in which ink is not discharged properly as it is supposed to be, could occur sometimes due to the clogging of its nozzle(s), which is caused by the thickening of ink, the adhesion of dust, among other reasons. Therefore, it is necessary to conduct periodical inspection of the operating conditions of nozzles to detect any abnormal discharge so as to check whether ink is discharged properly or not. Various kinds of abnormal discharge detection methods have been proposed to date. As an example thereof, an optical detection is carried out to check whether ink discharged from a nozzle shuts off a laser beam or not so as to recognize the presence/absence of properly discharged ink. (refer to Patent Document 1)
Cleaning is performed when any nozzle at which abnormal discharge occurs is detected. Such a malfunctioning nozzle will discharge ink properly after cleaning. Flushing and pump suction are known as typical examples of cleaning methods. (refer to Patent Document 2)
(Patent Document 1) Japanese Unexamined Patent Application Publication No. 2002-361863
(Patent Document 2) Japanese Unexamined Patent Application Publication No. 2004-299140